In order to shorten a waiting time until a printed material is outputted, image forming apparatuses such as a printer and an MFP (Multi Function Peripheral) execute controls so as to keep the temperature of a fixing unit thereof for fixing a toner image formed on a paper sheet to be constant, which results in large power consumption of the image forming apparatuses in a waiting state (normal mode). In view of that, an attempt to decrease the power consumption is practiced in the image forming apparatus by, when a nonuse state continues for a certain period, controlling the image forming apparatus to transition from a waiting state to a power saving state (power saving mode) in which less power is consumed than that in the waiting state.
On the other hand, in recent years, according to the prevalence of tablet terminals and smart-phones, not only a wired-network support but also a wireless-network support is requested to image forming apparatuses. To meet the request, image forming apparatuses are necessary to keep the waiting state such that a print request can be always accepted via a network. Even in a case where an image forming apparatus is going to transit into the power saving mode to stop power supply for certain functions, the image forming apparatus is not allowed to stop its network function to meet the request. Therefore, image forming apparatuses connectable to two lines of wired and wireless networks hardly provide sufficiently-decreased power consumption.
In view of these backgrounds, a proxy response method for use in a system including plural image forming apparatuses and a server has been proposed. In the method, the server or one of the image forming apparatus in a same network is assigned to be a base unit, and the other image forming apparatuses are operated in the power saving mode to accept only an activation request via a wired network, thus the power consumption of the total system is decreased, as disclose in Japanese Unexamined Patent Publication (JP-A) No. 2006-345102.
In this proxy response method, an image forming apparatus in which its wireless network function is working (an uprising base unit in the waiting state) receives a packet sent from a host apparatus (computer apparatus) toward another image forming apparatus (sub-unit) in the power saving state to make a proxy response. In case that the packet is a print request, the image forming apparatus as the uprising base unit sends an activation request via the wired network to the sub-unit, and the sub-unit executes printing after recovering from the power saving state. Thus, in the proxy response, since the image forming apparatuses other than the one base unit in the same network can keep the power saving state, the power consumption of the total system can be decreased.
Here, in a system where a host apparatus being a mobile terminal such as a tablet terminal and a smart-phone conducts wireless communications directly with image forming apparatuses without involving any repeater, conditions of the wireless communications are changeable according to the positional relationship between an image forming apparatus to be the base unit and the host apparatus. Therefore, in cases where the image forming apparatus to be the base unit and the host apparatus are positioned apart, or an obstruction exists between them, a communication error may occur on wireless communications between the image forming apparatus to be the base unit and the host apparatus, and the image forming apparatus to be the base unit can hardly execute instructions from the host apparatus properly.